Outlining chords with a scale sequence.
Here's a good hand workout—Bach's Invention #4 in D minor. There's a lot of scale work going on here, but there are some pretty cool melodic sequences that are outlining chords. Bach was a master of harmony in the Baroque era. He'd have two or more voicings moving independently in a horizontal direction. In other words, when single-note lines are stacked on top of one another, they create chords that we can see vertically. This is why even hearing just two independent voices playing a scale sequence, whether by 3rds or other groupings. You can hear an underlying harmony of chords. You can also hear this even with a single voice playing single notes that outline a chord sequence. The being of this piece is outlining two chords. Dm and C#°(diminish), he then points it out to us as he ascends to the octave to repeat the same motif. F A D is an inversion of Dm, G C# E is an inversion of C#°. Let's back up and look at the first two measures. We have a D harmonic minor scale ascending and descending. D E F G A Bb C# 1 2 b3 4 5 b6 7 However, he's not going up to the 7th degree; instead, he "pivots" the (C#) note down an octave. This is a saxophone technique. By pivoting a note up or down an octave, we can repeat a sequence, phrase, or line. So if we were playing a phrase that is out of range, we could pivot to a note an octave below and keep the phrase going. He then plays the two chords Dm and C#° to move up an octave, then repeats the motif from the first two measures. He then descends this pivot pattern down, they're moving in 4ths. Each note is moving in 4ths of some kind. F Bb E A, etc. Bb to E is an augmented 4th, a tritone interval. Which can lead us down another rabbit hole, but we'll skip that one for now. Each of those starting notes acts as a 3rd of a chord. F is the minor 3rd of Dm, Bb is the minor 3rd of Gm, E is a major 3rd of C, and A is the major 3rd of F. He's outlining Dm, Gm, C, and F. We could take this same idea with a typical scale sequence and pivot a note down an octave to outline chords. For example, a scale sequence in A major. By pivoting the 6th note in a scale down an octave, we'll be outlining some chords.